An Experimental Study on the Unsaturated Soil Parameters Changes due to Various Degree of Saturation

Abstract

Landslide is a natural disaster often occurring in Indonesia, associated with the rainy season. The slope failure mechanism is the main challenge in the slope stability analysis due to rainfall. The changing of the soil engineering properties under the effect of water infiltration during the rain should be fixed. In this study, the experimental studies were conducted to evaluate the unsaturated soil parameters changes, i.e., suction, cohesion, and internal friction angle, in various degrees of saturation. The filter paper tests were conducted to evaluate the matric suction of soil and develop the soil-water characteristic curve (SWCC) using the Soil Vision software. Fredlund and Xing, Van Genucthen, and Brooks and Corey fit the SWCC: The fitting equation developed by Fredlund and Xing resulted in the highest coefficient of determinant with R² of 0.91 and 0.97 for well-graded silty sand and silty sand curves, respectively. Thus, it was used to determine the correlation between saturation, cohesion, and matric suction. Shear strength parameters of soil samples were examined using a direct shear test method. The results show that the increase of the saturation degree reduces the soil suction and shear strength parameters. The result of this study is crucial to develop an understanding of the mechanism of slope failure.